The invention relates to an encoding or decoding circuit for time division multiplex and simultaneous or parallel signals, including shift registers having different write and read rates under the control of clock pulses of different frequencies, said shift registers forming part of a signal compression or signal expansion circuit, respectively, for encoding from simultaneous signals to the time division multiplex signal or for decoding from the time division multiplex signal to the simultaneous signals, respectively.
A circuit of this type is suitable for use in, for example, a transmission system which has been described in a public report "Experimental and Development Report 118/82" by the British "Independent Broadcasting Authority" (I.B.A.), entitled "MAC: A Television System for High-Quality Satellite Broadcasting". The report gives several variants for a so-called MAC (Multiplexed Analogue Component) picture coding. As is apparent from a survey table on page 9 of the report, it holds for all variants that the luminance and chrominance information in a television transmitter each undergo a time compression with the aid of a shift register, with the compression for the chrominance information being twice that of the luminance information. The chrominance information comprises two components per television line period and alternately one of the two occurs compressed in time in the time division multiplex coded signal. The luminance information associated with each line period is present in a time-compressed state in this signal. For the time compression associated with the luminance information the report gives the factors 2/3 and 3/4, leading to time compression factors of 1/3 and 3/8 for the chrominance information. The picture information per line period in the time division multiplex coded signal is sequentially composed of the time-compressed luminance information and one of the two associated time-compressed chrominance information components.
In a television receiver the time division multiplex coded signal is derived from the signal received through the transmission channel i.e. the satellite connection, which signal is applied to the associated decoding circuit including shift registers which supplies a time decompression or expansion for the luminance and chrominance information with the aid of synchronizing an identification information and which repeatedly supplies the expanded chrominance information over the subsequent line period.
Instead of a broadcasting transmitter it is feasible to use a consumer television camera which is connectable to a receiver suitable for use in the system described. In this case it is favorable for the sake of costs to have identical encoding and decoding circuits in which inputs and outputs are exchangeable whose encoding or decoding operation only depends on given connections to the circuit. The same applies to the use in tape or record recording and reproducing apparatus and/or transcodingn apparatus for time division multiplex signal transcoding.